Modern aircraft generally have a synthetic vision system “SVS”. This system enables presentation to the crew of a synthetic image of the outside view generally including piloting or navigation information. An SVS system includes a cartographic database representative of the overflown terrain, a geolocation system, electronic computation means, and one or more display devices installed in the cockpit of the aircraft. The geolocation system is of the global positioning system (GPS) type. It may be coupled to the inertial system of the machine. The geolocation system as a whole supplies at least the following parameters: position of the aircraft in terms of latitude, longitude and altitude and orientation of the aircraft in terms of pitch, roll and bearing and finally, accuracy of the location.
The image is generally displayed on the display screens that are located on the front of the instrument panel of the aircraft. It is a three-dimensional view of the outside represented in the most realistic possible manner. The point of view displayed is on the axis of the machine. This image is very attractive for the crew in that it provides them with a view of their environment that is close to reality and in particular a view of certain elements that are fundamental for navigation such as runways.
The representation is necessarily associated with an angle of view, also known as the field of view (FOV). This field of view is centered on the navigation direction of the vehicle. The FOV is not necessarily a simple choice. In effect, if the FOV is very large, distant details are represented with small dimensions, barely visible. If, on the other hand, the FOV is small, the details of interest are of significant size but can rapidly leave the field if they are not situated in the vicinity of the navigation axis of the machine. This problem is shown in FIGS. 1 and 2, which represent a three-dimensional synthetic view of the terrain including symbols that conventionally include an artificial horizon H and vertical bars indicating the altitude A and the speed V of the aircraft. The view includes a runway P that is in bold in the various figures. In FIG. 1, the FOV is large. The runway P appears as a small elongate quadrilateral, not necessarily easy for the user to distinguish. In FIG. 2 the FOV is small. It corresponds to the dashed outline rectangle in FIG. 1. The runway P is larger but is located at the edge of the field and is not necessarily easy for the pilot to identify.
To alleviate these drawbacks, various solutions have been proposed. Thus U.S. Pat. No. 8,159,416 entitled “Synthetic vision dynamic field of view” describes a vision system for aircraft in which the dimensions of the field of view depend automatically on navigation parameters depending, for example, on whether the aircraft is on the ground or in flight, its speed then varying considerably. This solution does not address the problem of objects situated outside the field of view. U.S. Pat. No. 7,218,245 entitled “Head-down aircraft attitude display and method for displaying schematic and terrain data symbology” describes a vision system for aircraft enabling display of simplified symbols representative of the terrain and symbols referenced to the trajectory of the aircraft. Once again, this solution fails to solve the problem of the presentation of three-dimensional objects of small size.